1. Field of the Invention
The present invention relates to a semiconductor device with an antenna used for a contactless IC card or the like and a fabrication method thereof.
2. Description of the Related Art
A contactless IC card, as shown in FIG. 11, comprises a semiconductor element 12 for sending and receiving signals, an antenna 10 in the form of a flat coil electrically connected to the semiconductor element 12, and card-like films 14 for holding the antenna 10 and the semiconductor element 12 from the two sides thereof, thereby forming a thin card as a whole.
The antenna 10 can be formed by pressing a thin metal sheet into a predetermined shape of a coil, or etching a conductive layer formed on one side of a film into a predetermined shape of coil.
The conventional contactless IC card, as shown in FIG. 11, has the antenna 10 arranged along the outer peripheral edge of the card. This arrangement is employed in view of the fact that the communication characteristics of the antenna 10 are determined by the area defined by the loop and the number of turns of the antenna, and also under the restraint of the size of a xe2x80x9ccardxe2x80x9d, the loop of the antenna 10 is formed along the outer peripheral edge while at the same time taking portability into account.
For example, the antenna can be formed by pressing or etching a thin metal sheet (e.g. an iron sheet) which is about 0.1 mm thick. In this case, the clearance between one antenna and an adjacent antenna usually ranges from 0.1 mm to 0.5 mm though it is generally determined by the number of turns of the antenna.
Also, the surface of the antenna formed as described above can be plated with nickel. Also, the surface of the portions of the antenna to which bonding wires are bonded, to electrically connect a semiconductor element and the antenna, can be plated with gold or palladium.
The requirement for a large area for the antenna 10 as in the conventional IC card, however, limits the possibility of reducing the size of the electronic devices and hence the applicability to other areas.
In view of the characteristics of electronic parts having such communication functions as described above, the object of the present invention is to provide a semiconductor device, and a preferred method of fabrication thereof, which can reduce the size of the electronic parts having such communication characteristics and are readily applicable to various electronic equipment.
In order to achieve the aforementioned object, the present invention is configured as described below.
According to one aspect of the invention, there is provided a semiconductor device with an antenna comprising one or more antenna units for sending and receiving signals, and a semiconductor element electrically connected to the antenna units, wherein the antenna units are formed by pressing or etching a thin metal sheet with substantially the same flat surface size as the semiconductor element, and the antenna units are integrally coupled to the surface of the semiconductor element.
The antenna units are formed in a size capable of being arranged within the surface of the semiconductor element and coupled to the surface of the semiconductor element.
The antenna units are formed in a plurality of layers, separated by insulating layers, and the antenna units formed on the respective layers are electrically connected in series with each other. By adjusting the number of the layers of the antenna unit, the required conditions such as the number of turns of the antenna can be met.
Also, the outer surface of the antenna is covered with a sealing resin.
Another feature of this invention is that connecting terminals protruded toward the antenna unit of an adjacent layer are formed on one of the surfaces of antenna units and the antenna units are electrically connected with each other through the connecting terminals.
Still another feature of the invention is that the antenna units are electrically connected with each other by using an anisotropic conductive adhesive film or an anisotropic conductive adhesive. The use of the anisotropic conductive adhesive film or the anisotropic conductive adhesive facilitates the electrical connection and integration between adjacent antenna layers.
According to another aspect of the invention, there is provided a method of fabricating a semiconductor device with an antenna comprising one or more antenna units for sending and receiving signals and a semiconductor element electrically connected with the antenna units, comprising the steps of forming a plurality of semiconductor elements at predetermined positions on a semiconductor wafer, forming an antenna frame having a plurality of antenna units at the positions corresponding to the predetermined positions by pressing or etching a thin metal sheet, and setting said semiconductor wafer and said antenna frame in register with each other in an opposed relation to each other in accordance with the positions of said semiconductor elements and said antenna units, coupling by connecting each of said semiconductor elements and the corresponding antenna units with each other electrically, and cutting off said semiconductor wafer and said antenna frame to the profile of each of said semiconductor devices.
Also, according to another aspect of the invention, there is provided a method of fabricating a semiconductor device with an antenna comprising one or more antenna units for sending and receiving signals and a semiconductor element electrically connected with the antenna units, comprising the steps of forming a plurality of semiconductor elements at predetermined positions on a semiconductor wafer, forming antenna frames, each of which has a plurality of antenna units at the positions corresponding of the predetermined positions, by pressing or etching a thin metal sheet, forming a multilayered member by integrating said antenna frames, each of which is separated by an adhesive film, and by connecting antenna units of said antenna frames electrically in series with each other, and setting said semiconductor wafer and said multilayered member in register with each other in an opposed relation to each other in accordance with the positions of said semiconductor elements and said antenna units, coupling by connecting each of said semiconductor elements and the corresponding antenna units with each other electrically, and cutting off said semiconductor wafer and said multilayered member to the profile of each of said semiconductor devices.
The antenna units of the antenna frames, each of which is separated by an adhesive film, are electrically connected in series with each other through the connecting terminals on a surface of the antenna unit formed into protrusions toward a surface of an adjacent antenna unit.
The outer surface of the antenna frame is covered with a sealing resin before the semiconductor wafer, having the antenna frame, is cut off to the profile of each of the semiconductor devices.